Simple Blackjack Program Error

[Demonstruck]

I have to write a program for my programming class. The assignment is thus:
Create a program that allows the user to type in cards in a dealer's hand, one at a time. If the user types in something that is not a valid card, notify them and do not include that input in the hand. Once they are done (either ask them how many cards they are entering or look for a special input such as a blank line, or a dash "-"), print out whether the dealer would stand or hit.

My program is this:

#include <iostream>
#include <string>
#include <vector>
#include <unordered_set>
#include <algorithm>
using namespace std;

bool card_validity_check(string card) {
	if ((card[0] == 'A' || (card[0] >= '2' && card[0] <= '9') || card[0] == '0' || card[0] == 'J' || card[0] == 'Q' || card[0] == 'K') && (card[1] == 'H' || card[1] == 'C' || card[1] == 'D' || card[1] == 'S')) {
		return true;
	} else {
		return false;
	}
}

int hand_value(vector<string> cards) {
	int total;
	total = 0;
	for (string card : cards) {
		switch (card[0]) {
		case 'A':
			if (total >= 17) {
				total += 1;
			}
			else if (total < 17) {
				total += 11;
			}
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':
			total += card[0] - '0';
		case '0':
		case 'J':
		case 'Q':
		case 'K':
			total += 10;
		}
		cout << total << endl;
	}
	return total;
}

bool stands(vector<string> hand){
	return 0;
}

int main() {
	vector<string> cards;
	string card;
entry:
	cout << "Enter a card for the dealer:" << endl;
	cin >> card;
	
	if (card_validity_check(card)) {
		cout << "This is a valid card" << endl;
		cards.push_back(card);
		cout << hand_value << endl;
	} else {
		cout << "This is not a valid card. Please retry." << endl;
		goto entry;
	}
	cin >> card;
}

I'm not entirely done with my program, but the program is currently supposed to, when you enter AH, output 11. In Visual Studio 2015, it outputs a string of letters and numbers. If anyone can point out my problem, that would be fantastic, thanks.

[cire]

hand_value is a function. Call it with an appropriate argument.

[Demonstruck]

THANK YOU. Nobody in my dorm could figure that out, thank you so much.